Free-Radical Ring-Opening Polymerization of Macrocyclic Aryl Ether Thioether Ketone Oligomers

Abstract

A facile free-radical ring-opening polymerization of macrocyclic aryl ether thioether ketone oligomers is described. Polymerization of the cyclic oligomers via a transthioetherification reaction to high molecular weight linear polymers is achieved both in the melt and in solution in the presence of a catalytic amount of elemental sulfur or 2,2‘-dithiobis(benzothiazole) (DTB). The free-radical nature of the polymerization reaction is indicated by electron paramagnetic resonance spectroscopy (EPR). The ring-opening polymerization reaction is unusual in that the molecular weight of the polymers obtained increases as the conversion of cyclic oligomers increases. The ring−chain equilibrium dramatically favors the formation of linear polymer, in which only low levels of cyclic materials are present after polymerization, even though the reaction is not enthalpically driven. The interchain equilibration is also a facile process during polymerization. This intermolecular transthioetherification is demonstrated by ...